The "Oracle compatability" project I suspect you're thinking of is called Fyracle, and can be found at http://www.janus-software.com/fb_fyracle.html. It takes care of many (most?) Oracle syntax oddities, and handles PL/SQL code so you don't lose investments in huge stored procedures. It sits as a front-end between you and Firebird.
I don't think Fyracle is open source/free, but I believe the runtime is free and the developers kit is cheap.
[No product endorsement intended here, I just am vaguely aware of the project.]
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The "Oracle compatability" project I suspect you're thinking of is called Fyracle, and can be found at http://www.janus-software.com/fb_fyracle.html. It takes care of many (most?) Oracle syntax oddities, and handles PL/SQL code so you don't lose investments in huge stored procedures. It sits as a front-end between you and Firebird. I don't think Fyracle is open source/free, but I believe the runtime is free and the developers kit is cheap. [No product endorsement intended here, I just am vaguely aware of the project.]